I've noticed
that the new "Complete Guide to Home Canning,"
Agriculture Information Bulletin No. 539, contains
recipes for making pickled products containing oil. I've
always been taught that oil should not be added to
home-canned food because it protects the spores of the
bacteria that cause botulism food poisoning.

You are right to be concerned. However, new research at
Pennsylvania State University has found that with safe,
tested recipes that contain a high level of acid, oil
can safely be added to some products. Acidifying foods
lowers the heat resistance of C. botulinum. The recipes
in the "Complete Guide to Home Canning," which can be
found on the
National
Center for Home Food Preservation website, have been
thoroughly tested and are safe. However, beware of
recipes from other sources. Check with your county
extension center before using them.